Suspensions of polymeric chlorotrifluoroethylene



Patented Oct. 20, 1953 SUSPENSIONS OF POLYMERIC CHLORO- TRIFLUOROETHYLENE Murray M. Sprung, Schenectady, N. Y., assignor to General Electric Company, a corporation of New York No Drawing. Original application November 25,

1949, Serial No. 129,532. Divided and this application January 16, 1953, Serial No. 331,729

V 14 Claims.

9 1 This application is a division of my earlier filed application, Serial No. 129,532, filed November 25, 1949, and assigned to the same assignee as the present invention.

This invention is concerned with suspensions of polymeric chlorotrifluoroethylene. More particularly, the invention relates to a suspension comprising (1) a dispersed phase of finely divided polymeric chlorotrifluoroethylene and (2) a dispersing medium comprising (a) an organic liquid or mixture of organic liquids which, at elevated temperatures but below their boiling points,

are solvents for the aforementioned polymer and (b) a liquid diluent which is a non-solvent for the polymer at any temperature and which is an oxygen-containing compound having a boiling point above 50 C. and selected from the class consisting of saturated aliphatic ethers (both straight-chained and cyclic), saturated aliphatic monohydric alcohols (including halogenated, e. g., chlorinated alcohols), aliphatic ketones, ali- 1 phatic esters, aliphatic lactones, aliphatic acetals, mixtures of monohydric saturated aliphatic alcoplications where such properties are desired. 7

Electrical conductors insulated with polymeric chlorotrifluoroethylene are capable of withstanding' temperatures of the order of from about 150 to 200 C. for long period of time with little change in the physical characteristics or of the insulating properties of the polymeric insulation. Such polymeric material is also highly desired for many applications Where its high softening point is an advantage. Thus, it is possible to mold various objects from the polymeric ch1orotrifluoroethylene, either with or without fillers to give useful articles which are dimensionally stable over a wide temperature range.

Because of its extreme chemical resistance and substantial insolubility in many of the common organic solvents, great difficulty has been experienced in obtaining the polymeric chlorotrifluoroethylene in usable form whereby it can be employed for coating or impregnating applications. Many attempts have been made to form solutions of the polymeric chlorotrifiuoroethylene, but these attempts have generally been unsuccessful because the limit of solubility of the polymeric chlorotrifluoroethylene in the solvent has been so small as to render it impractical. Attempts to prepare suspensions of polymeric chlorotrifluoroethylene have also been generally unsuccessful because of the poor stability of such suspensions in the dispersing mediums employed heretofore with polymeric chlorotrifluoroethylene.

I have now discovered for it is possible to make relatively stable suspensions of polymeric chloroetrifluoroethylene (any solid polymer thereof may be employed) using as the suspending medium a mixture of liquide described above in the first paragraph of this application. This is done by first grinding the polymeric material, for instance, in a micro-pulverizer, to a fine particle size and thereafter mixing the finely divided polymer with a dispersing phase comprising a mixture of ingredients comprising (a) an organic liquid which is a solvent for the polymer at an elevated temperature but below the boiling point 'of the liquid and (b) an oxygencontaining compound selected from the class described previously, and finally grinding this mixture, for example, in a pebble mill or a ball mill fora time sufficient to'yield a stable, uniform suspension.

Suspensions made in accordance with my above-described method are uniformly stable over long periods of time. I am able to prepare slower settling rates than those obtained from the first time that many other types of organic liquids. If there should be some slight settling out of the suspended polymeric material, it is possible by mere stirring, either before use or during use, to reinstate the suspension to its former acceptable state. Although some dispersions of similar polymers, e. g., polymeric tetrafluoroethylene, have been made using other materials as a dispersing phase, nevertheless, attempts to use these particular dispersing media with polymeric chlorotrifiuoroethylene have been generally unsuccessful.

Generally, the procedure followed for making my suspensions comprises pulverizing or grinding polymeric chlorotrifluoroethylene to a fine particle size of the, order of about 0.2 to 25 microns, preferably 0.5 to 15 microns. This may be accomplished by grinding the polymer in a micro-pulverizer used for such purposes. Thereafter, the finely ground polymerand the nirgture of liquids comprising the dispersing are mixed together and again ground, this time, for instance, in either a ball mill or a pebble mill. The ratio, by Weight, of dispersingphase and finely divided polymer may be carried within wide limits depending upon the desired egneentratiqn of the, i

final suspension. Thus, I may aduantageously employ, by weight, from 0.0,].- to 1 or more parts of the polymer per part of the liquid dispersing phase. A range which I have found useful comprises, by weight, from about 0.05 to 0.3 part polymen per part of the liquid dispersing phase. On a percentage basis, good results may be realizedwhen the polymer comprises about 10 to per cent,'by weight, of the totalweight of poly mer and the dispersing phase.

From the. foregoing general description it will be apparent that my invention employs both an active. solvent and a relativelyinexpensive, nonsolvent, diluent, thus permitting a considerable saving in money. The use ofa dispersing phase comprising a mixture of ingredients wherein one of: the ingredients is a solvent for the polymer at elevated temperatures, has several advantages. In the'first place, by using a relatively volatile rich-solvent diluent in the dispersing phase, this dilueiitflashe's off; first during the baking- 'cycle wher-i'the coated objeot is passed through a baking oven at elevated temperatures to efiect fusion or coalescence ofthe individual particle ofpolym'erifc"ohlorotrifiuoijoethylene deposited on the surfac "'I he aotive solvent or sol-vents remain mg injthe dispersing phase are then able to dissolvepr partially dissolve or to plasticize or swell the uniformlydeposited, finely divided particles of solid, polymeric chlorotrifluoroethylene. Sintering or fusionftherefore, ofthe individual polymerie'particlesoccurs at temperatureslower than arenorm ally required for the pure polymer. After fusion, the active solvents are preferably completely removed by further heating. The active (1. e., solvents in which the polymer is soluble at elevated temperatures) higher boiling solvents can "be recovered bymeans of a suitable recovery system; and retainedv foruse in making-additional suspensions.-

The, proportion, of active solvent in, the dis-.

persing phase may, of course, bevaried within,

ide im How ver o econ m cal. reasons L-have o nd p act caltou e a mi or p o orion, (a e," r m 5 to 3-. er cent. by we ght, r n t n e qmi t 1 p r en base -1 1 the v total weight of; the dispersing phase of such liquids. and m jor rop o si om tq 95.1 1. en irwish f; he i uid 1 izlr i i h iq y sr q PFQ Pi U-Q TQT ethylene) diluent. Variations within these ranges, e. g., from 5 to per cent of the active solvent and from 10 to per cent of the nonsolvent diluent, may be employed without departing from the scope of the invention.

The number of liquid active solvents or mixture of such materials which I have found can be employed in the practice of this invention are relativel few. Among these may be mentioned, for example, certain individual alkylated, preferably liquid, aromatic hydrocarbons, for instance, pseudocumene, mesitylene, t-butylbenzene, beta-methylnaphthalene, para-t-butyltoluene, alpha, beta-dimethylnaphthalene, amylbiphenyl, alpha-methyl, para-.methylstyrene, paracymene, distyrene (styrene dimer), diamylblphenyl, para-di-t-butylbenzene, etc.; certain high boiling organic esters, for instance, dibutyl phthalatc, dibutyl sebacate, butyl stearate, dibutyl adipabe, dioctyl sebacate, methyl stearate, tributyl citrate, tributyl tricarballylate, acetyl tributyl citrate, dihexyl tetrachlorophthalate, dioctyl tetrachlorophthalate (including its isomers,

e. g., di- (2-ethylhexyl) -tetrachlorophthalate) tr-isthrle lyco Qit y e at betananhthyl b ng ate, and mixtures thereof, etc.; fiuorinated organic compounds having a boiling point. above C. and selected from the class consisting of (a) nuclearly fluorinated aromatic hydrocarbons containing two aromatic nuclei free ofother substituents, ('b) halogenated (e. g., chlorinated, brominated, etc.) derivatives of lower alkayl-substituted (e. g., methyl, ethyl, propyl, isopropyl and butyl) aromatic hydrocarbons containing fluorine (e. g., from 1 to- 6 or more fluorines) in the alkyl substituent, (c) fluorinatedchlorinated aliphatic hydrocarbons of the C3 and C 4 series containing at least two chlorine atoms (e. g., from- 2 to- 6), (d) liquid low molecular weight polymers of chlorotrifluoroethylene (known as "-Fluorolubesw having the recurring structural unit (CF2CFCD12 where 11. is an integer equal tofrom 4 to 16, inclusive, etc. Mix;-

. turesof the foregoing materials may also be employed as will be apparent to those skilled in theart.

Additional examples of many of the active solyents; which may beemployed in the practice of invention may be found in my copending application Serial No. 'l29-,53 1 and in the joint copendingapplications of Frederick-O. Guenther and myself; SerialNos. 129,533 and 129,534,, all

filed November 25, 19 49, and assigned to the,

same assigneeas the present invention.

In order-thatthose skilled in the art may better understand; howthe present invention may be practiced, the following examples are given by way of illustration and not by way of limitation.

All parts are by weight.

Examp ior prop rtion, Qre-n n- OIV-en S forthe polymer and a. minorproportion were solvents for the polymer, at, elevated, temperatures. The follow, ing table shows the ingredients employed ii -making the suspensions. as, well: as the; proportions. of; ingredients, and the timethe-mixture of in;-

gredients was milledE tQ-Qhtam the suspensions,

TABLE I Weight of Weight Dispersing Milling Suspension No. Polymer, Dispersing Phase Phase Time, Parts 7 Components, Days Parts Fluorolube d 98 1 175 alpha-Fluoronaphthalene.- 147 3 -Butanol 580 Fluorolube 140 2 175 alpha-Fluoronaphtha 210 4. 7

-Butano1 475 Fluoroluba 98 3 175 alpha-Chloro 147 3 580 Fluorolub 98 4 176 Mesitylene 147 3 580 Fluorolube 98 6 R 175 alpha-Fluoronaphthalene. 147 5 n-Butanol 580 Fluorolube 132 7 B 165 a1pha-Fluoronaphthalene. 199 5. 7

n-Bntanol 504 Fluorolube 140 8 a 180 alpha-Fluoronaphthalene. 205

-Butano1 475 Fluorolube 98 9 a 175 alpha-Ohloronaphthalene. 147 5 n-Butanol 580 Fluorolube 131 10 a 180 alpha-Chloronaphthalena. 197 6, 7

-Butanol 492 Fluorolube. 98 11 n 175 Mesity1ene 147 5 n-ButanoL. 580 Fluorolube 90 12 n 160 Hexachlorobutadiene 135 5 -Butano1 615 Fluorolube 132 13 a 165 alpha-Fluoronaphtha1ene 199 4 -Hexano1 504 Fluorolube 132 14 a 165 a1pha-F1uoronaphthalene 199 4 2-Ethylhexanol 504 Fluorolube 132 15 b 165 alpha-Fluoronaphthal 199 5, 7

n-Butauol 504 Fluorolube. 98 16 b 175 Mesitylene. 147 V 5 n-Butan 580 Fluorolube. 100 17 b 150 t-Butyl ben 150 7 4. 8

-Butanc 600 Fluoroluba" 111 1g o 300 alpha-Fluoronaphthalenen 167 3 n-Butano1 422 The polymer employed in suspensions Nos. 1 to 5 had a no strength temperature of about 245 C.

* No strength temperature of about 270 C. b No strength temperature of about 305 C.

c This polymer was more finely divided than any of the three other polymers employed above and had a no strength temperature of about Low molecular weight polymer of chlorotrifluoroethylene and more particularly described in my copending application Serial No. 129,534.

The suspensions prepared above were all smooth, homogeneous and quite stable. In order to test the effect of using these suspensions as coatings for electrical conductors, a SZ-mill copper wire containing an outside thin layer of plated cadmium was passed through each suspension and thereafter into a vertical oven (the effective heated section was about three feet in height) maintained at an air temperature of about 350 to 425 C. The speed with which the conductor was passed through the suspension and the oven varied from about thirty seconds to approximately sixty seconds per pass. Each conductor was passed through the suspension and the oven five times in order to insure a good build-up of the insulating coating. The insulated conductors were then tested for abrasion resistance (using the method disclosed in the ap plication of Edward J. Flynn and Gerald W; Young, Serial No. 54,636, filed October 15, 1948,

and assigned to the same assignee as the present invention); insulation resistance, and dielectric strength. Thermal life measure at 250C. was

of the order of 20 to 30 hours. The following table shows representative results of these tests.

TABLE II V Abrasion Insulation Dielectric Suspension No. Resistance, Resistance Strength Strokes In Mercury (kv.) M

7 w 0. 9 14 w 0. 6 2 12 co 2. 2 2. 9 13 Q 2. 8 2. 8 7 a: 1. 2. 5 13 m 2. 4 2. 4 26 e0 1. 2 1. 8 4 m i 1. 7 3. 5 7 3 m 1. O 2. 2 2 0o 1. 6 2. 4 22 on 2. 5 2. 6 11 so 1. 7 2. 2 25 00 0.8 3. 4

It will, of course, be apparent to those skilled in the art that in addition to the compositions described above, other concentrations of polymeric chlorotrifiuoroethylene in the suspension may be employed without departing-from the 7 score of the invention. The various ratios of ingredients which can be advantageously employed have been disclosed previously.

In addition to the active solvents employed above, other such materials may also be .nsed, many examples of such solvents being more-particularly disclosed in my aforementioned applications filed concurrently herewith, which by reference are made part of the disclosures in the inglass cloth, glass batting, asbestos cloth, mica,-

etc. If desired, the-suspensions may be advan- 7 tageously employed in making molding -com-= g gqsitions by adding to the suspension various ert inor ani diner t tai a iqmoeeneu ,i liixture and thereafter removing-the solvent and non-so vent ii a hare n g ponents of the dispersing phase fromthe mixtur Laminated products ma also be p epar d stant application. by coating and impregnating sheet material and In addition to the known non-solvent diluents superposinglayerspfithe impregnated and coated employed in the examples above, I may use other material and pressing {the total assembly under oxygen-containing compounds having a boiling heat and pressure itaob a n :fllsing 9f E l p lypoint above 50 C. and selected from the class of mer and -to give-ahomogenous article. In some compounds mentioned in the first paragraph of 1,5 coatingapii icationsaspfor instance, in the coatthis specification. Among such compounds may ing of electrical-co ,GIQES, such as magnet wire, be mentioned, for instance, aliphatic ethers ((e. g., it has been.follndtadllantageous toadd varying diisopropyl ether, di-n-butyl ether, dioxane, amounts, for-examplajfrom one to ten per cent, tetrahydrofurane, 1,2-di-n-butoxy ethane, :etc.); by weight, nor more of ,a;finely ground pigment aliphatic monohydric alcohols (e. g., isobutyl 30 or filler to the suspensions. Among such pigalcohol, n-amyl alcohol, isoamyl alcohol, tertiary mentsland fillers,whicnmay be employed are, for amyl alcohol, 2-ethyl hexanol, chlorohydrin, example, -catalpa clay, bentonite, mica dust, etc); saturated aliphatic esters (e. g., methyl titanium dioxide, silica, -.lead silicate, lead acetate, ethyl acetate, ethylene glycol acetate, titanate,-etc. chloroethyl acetate, beta-methoxyethyl acetate, y claimedsuspensions.cent nsa methyl lactate, etc); aliphatic ketones (e. g., vents arerelatively=easy to use, and give products acetone, methyl ethyl ketone, methYl-I1-.p10py1 having good appearance and .a high degree of ketone, diacetone, etc); aliphatic acetals (e. g., clarity. Films -(e.;g {f;rom polymers having no dimethyl acetal, 1,3-dioxolane, dichloromethyl strengthjtemperaturesiof,from 240 to 2'70 C.) formal, bis-beta-methoxyethyl formal, etc); depositedfromthese suspensions on glass, for exaliphatic lactones (e. g., gamma-butyrolactcne, a p .we t ielea 1 931191 2 15 l d, on nuous, alpha-methyl, gamma-valerolactone, etc.) mixand strenglr n a ia mum fusion temtures of saturated aliphatic monohydric alcohols p lr fi 126 3. lllfk lfi being and dihydric aliphatic alcohols (e. g., including scribed-have-been reunit be eminently S ab e the saturated aliphatic monohydric alcohols for eatinewt r atex iibsn oni b fi s) mentioned above mixed with, for instance, ethylfor increasinethe s en t of e l te More ene glycol, trimethylene glycol, tetramethylene p uarantee-st en th;o zter atex. Wh ch no glycol, 2-methyl-2,4-pentanedio1, dipropylene sl l zstrsnet f about 240 to 0 glycol, etc.). Mixtures of any of the foregoing p. s. al wa imp o e :t I crosswise tensile known solvent diluents may also be employed if ,40 r z pq iz -r ll a lengthwise tensile desired. Many of the foregoing oxygen-containing compounds, as well as other such compounds and proportions of ingredients including theratio of dihydric to monohydric alcohol which may be employed in the practice of the present'invention, are more particularly disclosed in my application Serial No. 129,535 filed November 25, 1949, and assigned to the same assignee as the present invention.

Advantageously, the limit of the number of compounds, both non-solvent and solvent 'components, is dependent on the limits of miscibility of -.the components involved in the dispersing phase. .Little' di-fficult'y. has. been I encounteredein using any of the non-solvent components with the solvent componentsin the dispersing phase.

-In generaL'it is desirable to grind the -pulverized 7 solid polymer with the .liquid mixture comprising the dispersing phase .in a ball mill foruseveraLdays. However, for. purposes. .of. .5110". cessful application to magnet wire, it may not be ziecessarygto grind for more-than 24v to'lzhours, provided the original polymer has been reduced to the order of magnitude of at 'least G.2.to .25 -microns average particle size before grinding. No heating is necessary at any time for -making-the' suspensions. The time required for ball mill g-rinding toggive a satisfactory stable suspension may range from :about oneghalf to 1'5 fdaysmor more. .and,.. advantageously in thecase ointheiexamples -,described-,above, from about 1= 130510 days.

J-Ilhe suspen sionsiton-polymeric chlorotr-ifiuiorm ethylene described -.above may be employed 51in variousvways. {lib- 6y. mayebeeused for coating; and m regnating various fillers flush-13S} 012 examp strength .of ,IAGO ;p. when about 5 2%, by weight,polymer--bas e out the weight; of the terrateX, was .:added ;;by dipping t rate 1 1 1. suspensionand-baking in an oven.

"WhatjIclaim as'new'and 'desire'to secure by Letters Patent of the "United "K'SjlifiiflS f is:

l. A liquid suspension comprisingradispersed h-as iconsistins ic sent all of fi lg vid d. solidp high molecular weight polychlorotrifluoroethylene andta i pe s ng mediumef .thel o =polychlorotrifluoroethylene :comprising til) i an organic liquid which is a solvent for the aforesai s li polym r at.elera ...temperatu e but Whose .iso rent chara teri tic .i ef ec a t mperaturebelow. th boil epoint. o jithe li d, the af rem nti ned.liquid eine se e e rom. h cl .sonsistin -O .jdi nt l iphtha at Jdib eba at -bnt rstearate,; dinuity d pat 'dioet 'l s ha ate meth 'stearate ih ci r te, t iau ylitriear l late, .aeety rib y scitrat idinexin.tettaeniom n na te dio t .tetraehior h ha ate; triethylen l c die th lhex t and.httane hthilibenzn te.and 42 anon-s01- ventigliq id .ex e mc n ai n .d lnent having a boilin oint, ab .j'5 ,;c...,andse ecte irsini lass .nons s in f..satu ateda pha e saturated-ali hati .imon l yd i l oho s aturated i hatic gketones. sa r aliphatic esters, .7 mixtu es f ,m-on hydr s tur ted aliphatic-alcohols and dihydric saturatedaliphatic alcohols,, and. mixtures, of, the, foregoing oxygenconta nin -comm ne A 2. .Anliquid, suspension comprising (1) a. dispersed iqhase e onsistineee ser tial y,.of fin l vid d;-.-solid, hi h-molecula weiehtrp rs hl r trifiuoroethylene and (2) a dispersing medium for (1) comprising (a) dibutyl phthalate and (b) a liquid saturated aliphatic monohydric alcohol boiling above 50 C.

3. A liquid suspension comprising (1) a dispersed phase consisting essentially of finely divided, solid, high molecular weight polychlorotrifiuoroethylene and (2) a dispersing medium for (1) comprising (a) dibutyl phthalate and (b) a liquid saturated aliphatic ether boiling above 50 C.

4. A liquid suspension comprising (1) a dispersed phase consisting essentially of finely divided, solid, high molecular weight polychlorotrifluoroethylene and (2) a dispersing medium for (1) comprising (a) dibutyl phthalate and (b) a liquid saturated aliphatic acetal boiling above 50 C.

5. A liquid suspension comprising (1) a dispersed phase consisting essentially of finely divided, solid, high molecular weight polychlorotrifiuoroethylene and (2) a dispersing medium for (1) comprising (a) dibutyl phthalate and (b) a liquid saturated aliphatic ketone boiling above 50 C.

6. A liquid suspension comprising (1) a dispersed phase consisting essentially of finely divided, solid, high molecular weight polychlorotrifiuoroethylene as the sole polymeric ingredient in the solid state and (2) a dispersing medium for (1) comprising (a) dibutyl phthalate and (b) a mixture of a liquid monohydric saturated aliphatic alcohol and a liquid dihydric saturated aliphatic alcohol, both of the aforesaid alcohols boiling above 50 C.

7. A liquid suspension comprising (1) a dispersed phase consisting essentially of finely divided, solid, high molecular weight polychlorotrifiuoroethylene as the sole polymeric ingredient in the solid state and (2) a dispersing medium for (1) comprising (a) dibutyl phthalate and (b) n-butanol.

8. The method of making a stable suspension which comprises forming a mixture of ingredients comprising (1) a dispersed phase consisting essentially of finely divided, solid, high molecular weight polychlorotrifluoroethylene and (2) a dispersing medium from (1) comprising (a) an organic liquid which is a solvent for the aforesaid solid polymer at elevated temperatures but whose solvent characteristic is effective at a temperature below the boiling point of the liquid, the aforementioned liquid being selected from the class consisting of dibutyl phthalate, dibutyl sebacate, butyl stearate, dibutyl adipate, dioctyl sebacate, methyl stearate, tributyl citrate, tributyl tricarballylate, acetyl tributyl citrate, dihexyl tetrachlorophthalate, dioctyl tetrachlorophthalate, triethylene glycol di-(2-ethylhexoate) and beta-naphthyl benzoate, and (b) a non-solvent liquid oxygen-containing diluent having a boiling point above 50 C. and selected from the class consisting of saturated aliphatic ethers, saturated aliphatic monohydric alcohols, saturated aliphatic ketones, saturated aliphatic esters, mixtures of monohydric saturated i0 aliphatic alcohols and dihydric saturated aliphatic alcohols, and mixtures of the foregoing oxygen-containing compounds, and (2) grinding the aforementioned mixture of ingredients until a stable suspension is obtained.

9. The method of making a stable suspension which comprises (1) forming a mixture of ingredients comprising (a) finely divided, solid, high molecular weight polychlorotrifluoroethylene and (b) a dispersing medium for (a) comprising (A) dibutyl phthalate and (B) a liquid saturated aliphatic monohydric alcohol boiling above 50 0., and (2) grinding the aforementioned mixture of ingredients until a stable suspension is obtained.

10. The method of making a stable suspension which comprises (1) forming a mixture of ingredients comprising (a) finely divided, solid, high molecular weight polychlorotrifluoroethylene and (b) a dispersing medium for (a) comprising (A) dibutyl phthalate and (B) a liquid saturated aliphatic ether boiling above 50 C., and (2) grinding the aforementioned mixture of ingredients until a stable suspension is obtained.

11. The method of making a stable suspension which comprises (1) forming a mixture of ingredients comprising (a) finely divided, solid, high molecular weight polychlorotrifluoroethylene and (b) a dispersing medium for (a) comprising (A) dibutyl phthalate and (B) a liquid saturated aliphatic acetal boiling above 50 0., and (2) grinding the aforementioned mixture of ingredients until a stable suspension is obtained.

12. The method of making a stable suspension which comprises (1) forming a mixture of ingredients comprising (a) finely divided, solid, high molecular weight polychlorotrifiuoroethylene and (b) a dispersing medium for (a) comprising (A) dibutyl phthalate and (B) a liquid saturated aliphatic ketone boiling above 50 0., and (2) grinding the aforementioned mixture of ingredients until a stable suspension is obtained.

13. The method of making a stable suspension which comprises (1) forming a mixture of ingredients comprising (a) finely divided, solid, high molecular weight polychlorotrifluoroethylene as the sole polymeric ingredient in the solid state and (b) a dispersing medium for (a) comprising (A) dibutyl phthalate and (B) a mixture of a liquid monohydric saturated aliphatic alcohol and a liquid dihydric saturated aliphatic alcohol, both of the aforesaid alcohols boiling above 50 C., and (2) grinding the aforementioned mixture of ingredients until a stable suspension is obtained.

14. The method of making a stable suspension which comprises (1) forming amixture of ingredients comprising (a) finely divided, solid, high molecular weight polychlorotrifiuoroethylene and (b) a dispersing medium for (a) comprising (A) dibutyl phthalate and (B) n-butanol, and (2) grinding the aforementioned mixture of ingredients until a stable suspension is obtained.

MURRAY M. SPRUNG.

No references cited. 

1. A LIQUID SUSPENSION COMPRISING A DISPERSED PHASE CONSISTING ESSENTIALLY OF FINELY DIVIDED, SOLID, HIGH MOLECULAR WEIGHT POLYCHLOROTRIFLUOROETHYLENE AND A DISPERSING MEDIUM FOR THE SOLID POLYCHLOROTRIFLUOROETHYLENE COMPRISING (1) AN ORGANIC LIQUID WHICH IS A SOLVENT FOR THE AFORESAID SOLID POLYMER AT ELEVATED TEMPERATURES BUT WHOSE SOLVENT CHARACTERISTIC IS EFFECTIVE AT A TEMPERATURE BELOW THE BOILING POINT OF THE LIQUID, THE AFOREMENTIONED LIQUID BEING SELECTED FROM THE CLASS CONSISTING OF DIBUTYL PHTHALATE, DIBUTYL SEBACATE, BUTYL STEARATE, DIBUTYL, ADIPATE, DIOCTYL SEBACATE, METHYL STEARATE, TRIBUTYL CITRATE, TRIBUTYL TRICARBALLYLATE, ACETYL TRIBUTYL CITRATE, DIHEXYL TETRACHLOROPHTHALATE, DIOCTYL TETRACHLOROPHTHALATE, TRIETHYLENE GLYCOL DI-(2-ETHYLHEXOATE), AND BETA-NAPHTHYL BENZOATE, AND (2) A NON-SOLVENT LIQUID OXYGEN-CONTAINING DILUENT HAVING A BOILING POINT ABOVE 50* C. AND SELECTED FROM THE CLASS CONSISTING OF SATURATED ALIPHATIC ETHERS, SATURATED ALIPHATIC MONOHYDRIC ALCOHOLS, SATURATED ALIPHATIC KETONES, SATURATED ALIPHATIC ESTERS, MIXTURES OF MONOHYDRIC SATURATED ALIPHATIC ALCOHOLS AND DIHYDRIC SATURATED ALIPHATIC ALCOHOLS, AND MIXTURES OF THE FOREGOING OXYGENCONTAINING COMPOUNDS. 